Rice Lake is a lake located in south-eastern Ontario, in Northumberland County and Peterborough County. The lake is located south of the City of Peterborough and the Kawartha lakes (Ontario) and north of Cobourg and is part of the Trent-Severn Waterway, which flows into the lake by the Otonabee and out via the Trent. It is 32 km long and 5 km wide.